The invention relates to a device for locking the steering column of a motor vehicle steering mechanism, with a locking device arranged within the zone of the steering column, and a central controller electrically connected to said locking device.
Such a device is described, for example in German patent application No. 199 06 267.6, which has not been published on an earlier date. The locking device described in said application comprises an electric servo-drive for displacing a locking element from its locking into its unlocking position, and vice versa, as well as a sensor for monitoring the position of the locking element or of a safety element securing said locking element. In the locking position, the locking element engages the recess of a toothed rim secured on the steering column, said recess being formed by adjacent teeth, and blocks the steering column in that way.
The locking device described in patent application 199 06 267.6 has an electronic circuit device both for controlling the servo-drive and evaluating the measuring signals generated by the sensor, said circuit being connected to the central controller of the motor vehicle via electrical cables. No details are specified in said application with respect to any control of the locking device with the help of the central controller. It was found to be advantageous in practical life if, while the motor vehicle is moving, the safety element is retained not only in its unlocking position, for example by a spring-actuated safety element, but if the supply voltage of the locking device is additionally switched off by means of the central controller. This assures that the locking element cannot be displaced in any safety-critical direction by the electrically driven setting member (e.g. an electric motor) in the presence of an electrical malfunction.
It was found that it is a drawback with such an electrical shutdown of the locking device that the changes in conditions which the sensor is expected to monitor such as, for example, occurrence of breakage of the housing or breakage of the spring in the spring actuated safety element (or also manipulation on the locking device), cannot be detected while the motor vehicle is moving. This may under certain circumstances lead to dangerous situations for the driver of the vehicle.
Furthermore, a device for locking the steering column of the steering mechanisms of a motor vehicle is known from DE 198 09 295 C1, which comprises a locking bar that is displaceable by an electrical setting member. So as to be able to assure that the unlocking and locking positions of the locking bar can be detected with very high accuracy in a simple manner, the invention proposes that use be made of at least two independently operating sensors which are electrically connected to an electronic circuit device acting on the setting member. The first sensor detects in this connection the position of a safety element, which engages a recess of the locking bar. The second sensor is directly associated with the locking bar and always responds to an element arranged on the locking bar in such a way as to be detected when the locking bar is in its locking position.
A theft protection system for motor vehicles is known from DE 197 37 856 A1 which has one single controlling unit on the side of the lock. Together with a steering lock system said controlling unit is arranged in a safety housing near the steering wheel. The controlling unit unlocks the steering locking system and releases the drive-away blockage if authorization has been successfully verified by a code signal transmitter.
Finally, a device for locking the steering column of a motor vehicle steering mechanism is known from EP 846 602 A2, where the position of a safety element is detected by means of a switch, said safety element securing the locking bar in the unlocking position, whereby the latter can be swiveled by an electrical setting member. Both the switch and the setting member are connected to an electronic circuit device via electrical cables.
The invention is based on the problem of proposing a device of the type specified above, by means of which the monitoring of the condition with the sensor arranged in the locking device is possible also while the vehicle is in motion without causing thereby any increase in the safety risk for the driver of the vehicle.
The problem is solved according to the invention by the features of the claims, and particularly advantageous features of the invention are discloded in the dependent claims.
The invention is substantially based on the idea that the sensor is connected not only to the electronic circuit of the locking device, but additionally also to the central controller, in a way such that even if the supply voltage for the locking device is switched off, the controller is still capable of scanning and evaluating the status of the locking device detected by the sensor.
The sensor is advantageously a position sensor (e.g. a Hall sensor) that monitors the position of the locking element and/or of a safety element securing said locking element.
The electrical setting member may be both an electric motor with gearing connected downstream, or a lifting magnet that is connected with the locking element, or whose displaceable tappet forms the locking element.
A further benefit of using such a status sensor that is additionally connectable also to the central controller is that the function of the locking device can be tested in a simple way. For this purpose, test signals are generated by means of the central controller and transmitted to the status sensor by way of the additional line (for example, if a Hall sensor is employed, a defined current is adjusted, or the supply current of the Hall sensor is switched off). Such artificially generated sensor signals are subsequently evaluated by the electronic circuit of the locking device or by the central controller connected downstream (test loop).